Accordingly to the in silico results, we decided to sequence 1500 bp of the 5' region, intron 1 and intron 2 of SERPINC1, regions containing the potential VDRE regions, in 23 patients with antithrombin deficiency without mutations in coding exons and flanking regions or gross gene defects. Here, SERPINC1 is linked to hereditary antithrombin deficiency.